A brief history of astronomy
How has our understanding of space developed over the past 5,000 years? Here are nine key moments in the history of humankind's understanding of the universe, from the biggest of bangs to the dawning realisation that not everything revolves around us on Earth
“If I have seen further than other men, it is by standing on the shoulders of giants.”
So wrote Isaac Newton on 5 February 1676. In one stroke, Newton encapsulated the entire history of astronomy. It is an edifice built on the endeavours of countless men and women through the millennia; a vast pyramid of human achievement that points towards the sky.
The history of astronomy is so much more than the history of a science – it is a profound collection of humankind’s cultures; its ideas and ideals. Why else would we call the cosmic firmament “heaven”, and populate it with deities like Apollo, the Sun god; Mars, the bringer of war; and Jupiter, the king of gods?
Our ancestors built celestial monuments – from Stonehenge to the great Pyramids. Are these cathedrals to the cosmos? The sky was as much a landscape to our ancient forebears as our countryside is to us today. There was no division between Earth and the stars.
Here's are nine ways how our understanding of space has developed over the past 5,000 years.
Time and place
Midsummer sunrise at Stonehenge is so iconic that the place swarms with New Agers and latter day Druids watching the Sun climb above the Heel Stone. However, research suggests the Druids’ ancient predecessors watched the Sun set from the Heel Stone on midwinter’s day. Either way, Stonehenge marks the extremes of the calendar.
- Read more | The secrets of Stonehenge: how was it built?
Even more impressive is the 300 BC monument at Chankillo, Peru, where a line of 13 towers marks points at which the Sun rises throughout the year. Yet preliterate civilisations didn’t just keep time by the heavens: the Polynesians used the stars to navigate from Hawaii to New Zealand – a distance of 7,000km – out of sight of land.
Mirror of the Earth
Chinese astronomers were the first to make accurate records of the sky. They regarded the heavens as a mirror of the Earth, with the stars representing different regions of China. So an exploding star in a star pattern would indicate a rebellion in a corresponding province.
We have Chinese astronomers to thank for the earliest known records of Halley’s Comet – in 240 BC – and an account of a supernova, from AD 1054, whose remains today form a tangled mass of gas called the Crab Nebula.
Ordering the heavens
The Greek philosopher Pythagoras was among the first to question the widely held view that the world was flat when, in the sixth century BC, he taught that the Earth must be a sphere, because of the shape of its shadow on the Moon during a lunar eclipse.
Over 200 years later Aristarchus suggested the Earth moves round the Sun – yet his idea didn’t take off.
- Read more | Who’s who in ancient Greece? Meet 14 famous Greeks
Instead, it was left to Ptolemy to leave the ancient Greeks’ most lasting imprint on astronomy when (around AD 150) he concluded that the planets moved on small circles around the central Earth, which moved around a larger circle. His theory was unchallenged for 1,400 years.
The Earth moves
Our perception of mankind’s importance in the Universe changed forever in 1543, when Polish canon Nicolaus Copernicus published a book arguing that the Earth did not sit at its centre. Instead, it was merely a planet orbiting the Sun.
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Copernicus had come to this conclusion over 30 years earlier, but he largely kept it to himself. His case was proven in 1610, when Galileo Galilei – in Padua, Italy – turned his telescope to the skies.
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Galileo saw that Jupiter was accompanied by four moons (overturning the argument that the Earth couldn’t be in motion as it would leave the Moon behind) and observed the changing phases of Venus, which showed this planet must be orbiting the Sun.
The church banned Galileo’s books, but from then on, no one seriously doubted that the Earth had been dethroned from the centre of the Universe.
A matter of some gravity
While the University of Cambridge was closed due to the plague in 1665, Isaac Newton returned home to Woolsthorpe Manor, Lincolnshire, where he formulated the law of gravity – which stipulates how every body in the Universe attracts every other.
But he didn’t publish it until persuaded to by Edmond Halley, who used Newton’s law to calculate that comets seen in 1531, 1607 and 1682 were the same visitor. And it was this law that led Halley to predict the return in 1758 of the comet that bears his name.
On 13 March 1781, a German amateur astronomer living in Bath doubled the size of the Solar System. William Herschel discovered a “curious either nebulous star or comet” – which turned out to be a planet twice as far from the Sun as Saturn.
Herschel wanted to name it Georgium Sidus, after King George III, but the name Uranus was internationally accepted.
Over the decades, astronomers found that Uranus was being pulled by the gravity of a more distant planet, leading to the discovery of Neptune in 1846. Pluto, discovered in 1930, was at first called a planet but, uniquely in history, its status as a planet was revoked in 2006.
Powerhouse of the stars
“On the subject of stars… we shall never be able by any means to study their chemical composition.”
So wrote the French positivist philosopher Auguste Comte in 1835. But only two decades later, German chemists Gustav Kirchhoff and Robert Bunsen proved him wrong. They identified elements in the Sun by comparing the dark lines in its spectrum of colours with laboratory spectra of elements, such as hydrogen and iron.
In the 1920s British astronomer Cecilia Payne worked out the relative proportions of the elements, and proved most of the Universe is made of hydrogen. It led to an understanding that the powerhouse of the stars was basically a hydrogen bomb running in slow motion.
Astrophysicist Fred Hoyle squared the circle by showing how elements are built up in stars. So the gold in your wedding ring is nothing less than the product of an exploding star.
The Big Bang
In the 1920s, American astronomer Edwin Hubble, along with former mule-driver Milton Humason, found that galaxies are racing apart from each other. The Universe is expanding, suggested Belgian priest Georges Lemaitre, because it was born in an exploding “primeval atom” – what we now call the Big Bang.
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This was proved in 1965, when American scientists Arno Penzias and Robert Wilson discovered a faint background of radio waves – the afterglow of the Big Bang.
Blacker than night
British army scientist Stanley Hey was perplexed in February 1942. He was investigating what seemed to be an outburst of German radar jamming – but it moved around the sky during the day. Hey realised the emission came from the Sun, and instigated the science of radio astronomy.
Since then, radio astronomers have discovered pulsars – dense balls of matter only the size of a city, but with the mass of the Sun. And they have found giant black holes.
These cosmic monsters weigh as much as a billion suns, and their gravity is so powerful that light can’t escape.
As the gas from the stars swirls round the black hole, it shines as brilliantly as hundreds of galaxies in an incandescent flickering maelstrom that astronomers call a quasar.
This article was written by the late astronomer and broadcaster Heather Couper. Among her radio credits, she wrote and presented the BBC Radio 4 series Cosmic Quest. As an author, she wrote more than 40 books on space and astronomy, including The History of Astronomy (Cassell Illustrated, 2007), co-authored with Nigel Henbest.
This content first published in the June 2008 edition of BBC History Magazine
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